If you have looked into weight loss medication and come away confused, that is not your fault. There are two entirely separate sets of rules operating at the same time, and most of what you will read online only explains one of them.
Understanding the difference is the single most useful thing you can do before speaking to anyone — a GP or a private provider.
The two systems
What NICE says. The National Institute for Health and Care Excellence assesses which treatments the NHS should offer and to whom. Its criteria are clinical.
What the NHS will actually pay for. NHS England decides how quickly those recommendations can be afforded. Right now, that is much slower than the criteria suggest.
Under NICE’s recommendation for tirzepatide, around 3.4 million people in England would qualify. NHS England requested and was granted a variation to phase this in: roughly 220,000 people over the first three years, with the full eligible population expected to have access within a maximum of 12 years.
So it is entirely possible — common, in fact — to meet NICE’s clinical criteria and still not be able to get treatment from your GP this year, or for several years.
NHS eligibility: what your GP can prescribe
For a GP in England to prescribe tirzepatide for weight management right now, you need both:
- a BMI of 35 or above, and
- at least four qualifying health conditions
From April 2027 this widens to include people with a BMI of 40 or above who have three qualifying conditions.
The four-condition rule is stricter than it sounds
Only five conditions count toward this total, and each has a specific medical definition:
| Condition | What counts |
|---|---|
| High blood pressure | Diagnosed, and you take medication for it |
| Cholesterol or lipid problems | You take lipid-lowering medication, or your blood test results meet set thresholds |
| Obstructive sleep apnoea | Confirmed by a sleep study, and you meet the criteria for CPAP treatment |
| Cardiovascular disease | Established heart or circulatory disease — for example angina, a previous heart attack, stroke, or peripheral vascular disease |
| Type 2 diabetes | Diagnosed type 2 diabetes |
Notice what is not on this list: fatty liver disease, PCOS, prediabetes, arthritis, and depression. These are all genuinely weight-related, and they may count elsewhere — but they do not count toward the four needed for GP prescribing.
Note also that having a condition is not enough on its own. Untreated high blood pressure, or suspected but unconfirmed sleep apnoea, will not count. This catches a lot of people out.
If you are from certain ethnic backgrounds, the threshold is lower
BMI thresholds are reduced by 2.5 for people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds. This is because health risks associated with excess weight tend to appear at a lower BMI in these groups.
In practice, a BMI of 35 becomes 32.5, and 40 becomes 37.5. Your BMI does not change — the bar does.
The specialist route
The cohort restrictions above apply to GP prescribing. Specialist weight management services work differently: they are funded for everyone who meets NICE’s full criteria, which for tirzepatide is a BMI of 35 or above with at least one weight-related condition.
That sounds like a much wider door, and on paper it is. In practice:
- you need a referral, usually from your GP
- local health boards are permitted to apply the same cohort restrictions if they choose
- waiting lists vary enormously by area, and can be long
It is still worth asking about. Ask your GP practice specifically what has been commissioned in your area, because the position genuinely differs from place to place.
Semaglutide injections are also available through specialist services, under different rules: at least one weight-related condition plus a BMI of 35 or above, or a BMI of 30–34.9 if you also meet the criteria for specialist referral. Unlike tirzepatide, it is limited to a maximum of two years.
Support comes with the medicine, not instead of it
This is easy to miss and genuinely important. NHS treatment must be provided alongside wraparound care — nutritional and dietary advice as a minimum, plus behavioural support. In primary care this runs for at least nine months from when you start.
You should also expect monthly face-to-face appointments while your dose is being increased, and structured medication reviews for at least the first year.
If a service is offering you medication with no support attached, that falls short of what the NHS considers the standard of care.
Private eligibility: a much wider door
Private providers prescribe according to the medicine’s licence rather than NICE’s criteria. Every licensed weight management medicine in the UK uses the same threshold:
- a BMI of 30 or above, or
- a BMI of 27 to 30 with at least one weight-related health condition
Here, “weight-related condition” is interpreted much more broadly. Conditions that do not count toward NHS cohort eligibility — including PCOS, prediabetes and fatty liver disease — may well count here. There is no fixed list; a prescriber assesses it.
The licence itself does not include the 2.5 BMI adjustment for ethnicity, although some providers apply it anyway as good practice.
Meeting these criteria does not guarantee a prescription. A registered prescriber must assess your individual suitability, and should be verifying what you tell them independently — through your medical records or by contacting your GP — rather than relying on an online questionnaire alone.
The one-way door: private treatment does not transfer to the NHS
If you take one thing from this guide, take this.
Treatment started privately cannot be continued by an NHS GP. If you begin privately and later become eligible for NHS treatment, you do not carry your prescription across. You would need to meet the NICE criteria, be referred to a specialist service, and start the NHS pathway from the beginning.
Going private does not disqualify you from future NHS treatment. But it does not give you a head start either, and it does not shorten any queue.
This matters because the decision to start privately is, in practice, a decision to fund your own treatment for as long as you continue it — including as your dose increases and the cost goes up. It is worth thinking about the full cost over a year or more, not just the first month.
What about the new tablets?
Two GLP-1 tablets have now been licensed in the UK for weight management: oral semaglutide, approved in June 2026, and orforglipron, approved in August 2026. Both use the same eligibility thresholds as the injections.
Neither is currently available on the NHS. NHS funding requires a separate NICE assessment, and those are still in progress.
What is changing
Two things worth watching:
GP incentives. From April 2026, GP practices have new targets around identifying people living with obesity and considering weight management treatment. You may find your practice raises the subject with you before you raise it with them.
A formal review. NICE will review how the phased rollout is going within three years of its original decision, and an independent evaluation is underway. That review is the most likely route to the timeline shortening.
This explains published NHS, NICE and regulatory criteria so you can understand where you stand. It is not medical advice, and it cannot tell you whether treatment is suitable or safe for you — only a registered prescriber can do that after assessing you individually.
Weight loss medication is not suitable during pregnancy or if you are planning a pregnancy, and there are specific contraception precautions to discuss. If you have a history of an eating disorder, raise this with a clinician before starting any treatment.